Email rejections due to DMARC

[Simon Lloyd]

You need to add an "allow" or "include" to to your spf record for the domain like this:
a:vbulletin.org include:vbulletin.org
That allows the domain as a sender, i personally haven't had any issues with the email sending as i dont allow my users to use the email to a friend function or contact them by email but i'm guessing you'll have to add every domain that your users use.